#include <bits/stdc++.h>
using namespace std;

#define int int64_t
#define endl "\n"

using PII = pair<int, int>;
using TII = tuple<int, int, int>;
template<class T> using V = vector<T>;
using i64 = long long;
using i128 = __int128;
using u64 = unsigned long long;

#define FOR(i, a, b) for (int i = (int)(a); i <= (int)(b); i++)
#define FOR2(i, a, b, c) for (int i = (int)(a); i <= (int)(b); i += c)
#define FORD(i, b, a) for (int i = (int)(a); i >= (int)(b); i--)
#define FORD2(i, b, a, c) for (int i = (int)(a); i >= (int)(b); i -= c)
#define ALL(a) a.begin(), a.end()
#define RALL(a) a.rbegin(), a.rend()
#define lowbit(x) ((x) & (-x))
#define RE return;
#define Yes cout << "Yes" << endl;
#define YES cout << "YES" << endl;
#define No cout << "No" << endl;
#define NO cout << "NO" << endl;
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define sz(x) (int)(x).size()

void solve() {
    int n;
    cin >> n;
    V<int> w(n + 1, 0);
    map<int, int> mp;
    FOR(i, 1, n) cin >> w[i], mp[w[i]]++;

    int cnt = 0;
    set<int> s;
    FOR(i, 1, n) {
        if (!mp[i]) {
            cnt++;
            s.insert(i);
        }
    }
    cout << (n - cnt) << endl;

    FOR(i, 1, n) {
        if (mp[w[i]] > 1) {
            mp[w[i]]--;
            auto it = s.upper_bound(i);
            if (it != s.end()) {
                if (*it == i) {
                    cout << w[i] << ' ';
                    mp[w[i]]++;
                    continue;
                }
                cout << *it << ' ';
                s.erase(s.find(*it));
            } else {
                if (it != s.begin()) {
                    it--;
                    if (*it == i) {
                        cout << w[i] << ' ';
                        mp[w[i]]++;
                        continue;
                    }

                    cout << *it << ' ';
                    s.erase(s.find(*it));
                }
            }
        } else {
            cout << w[i] << " ";
        }
    }
    cout << endl;
}

signed main() {
    int Task = 1;

    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> Task;
    while (Task--) {
        solve();
    }

    return 0;
}
